1. Field of the Invention
The present invention relates to a cable modem performing channel bonding, and more particularly, to a cable modem transmitting in an upstream in a Hybrid Fiber Coaxial (HFC) network.
2. Description of Related Art
A Data Over Cable Service Interface Specification (DOCSIS) 3.0 has been provided. This standard may support a downlink transmission rate of 150 Mbps and an uplink transmission rate of over 120 Mbps in a Hybrid Fiber Coaxial (HFC) network.
A channel bonding technology is used to increase an uplink transmission speed up to over 120 Mbps. That is, a channel bonding technology may enable a plurality of independent channels to be channel-bonded to a single channel, and enable a cable modem to achieve a higher transmission speed using the bonded channel.
A general cable modem may transmit upstream by modulating source data, converting digital data to an analog signal, and generating an output signal with a radio frequency using the converted analog signal. Also, a general cable modem may require a plurality of analog-frequency converters to generate an output signal with a radio frequency using a converted analog signal.
However, a plurality of analog-frequency converters may cause the increase in complexity of a cable modem. Also, an error generated when the plurality of analog-frequency converters converts a frequency may not be significantly reduced.